The Touch of Death does not exist, that far has been proven. Rather, these instances of "instant death blows" can be explained by inhuman accuracy in the dealing of heavy blows to exposed nerve centers of the body. The temples, the back of the head, soft parts of the neck, etc. In other words, it has nothing to do with body energy or qi, but rather a mastery of the martial arts. Styles that emphasize force such as the Tiger can kill someone just as surely as the Crane style, it just takes a bit longer to bludgeon someone to death than one, single deadly blow to vulnerable areas. I suspect there must be luck involved, no skilled martial artist would allow his vulnerabilities to be exposed for a single instant, never mind long enough for a strike to contact.

As for the beneficial aspects of dim mak, it already exists in the form of Chinese massage and other therapies based on the manipulation of nerves and qi. Practitioners would gouge their fingers into sensitive nerve spots around the body, causing immense amounts of pain (I know because I've sat through it), but afterwards one would feel much more refreshed, full of vitality. I don't know how it works, but it has something to do with qi, nerve centers, and body balance.